A seat belt device in which an electric motor rotates a spindle to wind a webbing when necessary, whereby an occupant is held in a seat is known and referenced herein as a conventional seat belt device (see, e.g., Patent Document 1). In the conventional seat belt device, a clutch is provided in a retractor. The clutch is released when the occupant draws out and fastens the webbing upon riding on a vehicle, whereby a drawing-out resistance of the webbing is generally in a lowered state.
In a seat belt device having a retractor which winds the webbing by a winding spring, a winding force of the winding spring that has been set to be strong to some extent is set to be very weak in advance, whereby the webbing is easily drawn out and any feeling of pressure from the webbing is decreased while fastening the webbing.
However, in such a seat belt device, since the winding force of the winding spring is weak, it is difficult to completely store the webbing due to a friction between a D-ring and the webbing or due to a weight of a tongue. Thus, in such a seat belt device, there has been proposed to assist a winding by using a motor at the time of the storage. More specifically, when the motor rotates in a winding direction, the clutch is set to a power transmittable state and thus the winding assistance is made possible. When the storage is completed, the motor stops assisting the winding and rotates in a direction opposite to the winding direction, whereby the clutch is set to a power transmission disabled state and returns in the original state, and thus the webbing is only forced by a weak webbing force of the winding spring.
Patent Document 1: Japanese Patent Unexamined Publication No. 2001-163185